The present invention relates to apparatus for controlling the automatic opening and closing of doors. Known arrangements for control of automatically opened doors includes sensors which sense either the present or the movement of an object or person in the vicinity of the door. Such sensors include photocell detectors and doppler radar detectors.
According to known arrangements, the doppler radar senses movement of a person toward the door which triggers the opening of the door. The door is usually closed by operation of an automatic timing circuit, which holds the door in a fully opened position for a pre-selected time, this is usually generously allotted so that a slow moving person will have time to pass through the door. It will be recognized that it is desirable that the door not be opened for too long a period, because of the resulting loss of heat or air conditioning to the building. Present arrangements for automatic closing of the door usually rely on photocell or floormat detection of the passage of a person, for purposes of providing a closing operation.
Operational difficulties are encountered in such prior art systems in the event a person walks toward the door, is detected by the doppler radar to open the door, and then walks away without passing through the door. In this case, the prior art systems do not detect the passage of the person through the door and the door remains open until closed by an automatic time circuit.
Another difficulty with such prior art systems arises when a door is situated along a frequently used walk. The doppler radar may detect the motion of a person in a direction generally traverse to door opening, causing the door to open. Again, since the person does not pass through the door, the door remains opened for an unduly long period of time.
It is an object of the present invention to provide a new and improved arrangement of sensing devices and control circuits for detecting the movement of objects and persons and controlling operation of an automatic door.
It is an object of the invention to provide such an arrangement which solves the problems associated with prior art devices in situations where a person walks toward a door opening, is detected, and then does not pass through the door opening.